Studying the stellar mass , age , luminosity , star-formation rate , and impact parameter of quasar absorber host galaxies can aid in the understanding of galaxy formation and evolution as well as in testing their models .
We derive the Spectral Energy Distribution ( SED ) and impact parameter limits of low redshift ( z _ { abs } = 0.37 - 0.55 ) Mg II absorbers and of higher redshift ( z _ { abs } = 1.0 - 2.5 ) 2175 Å dust absorbers ( 2DAs ) .
We use an imaging stacking technique to statistically boost the signal-to-noise ratio ( SNR ) to increase detection of the absorber host galaxies .
The point spread function of the background quasar is modeled with Principal Component Analysis ( PCA ) .
This method efficiently reduces the uncertainty of traditional PSF modeling .
Our SED for Mg II absorbers indicates that low redshift Mg II absorber host galaxies are likely star-forming galaxies transitioning into red quiescent galaxies , with a low star formation rate of 2.2 M _ { \odot } yr ^ { -1 } .
From the stacked images and simulations , we show that the average impact parameter of 2DAs is > 5 times smaller than that of Mg II absorbers , at < 7 kpc instead of Mg II absorbers ’ 48 kpc , indicating that 2DAs are likely associated with disk components of high redshift galaxies .
This means that 2DAs are likely good probes to study precursors to the Milky Way .